The huge engines that powered the first stage of the Saturn 5 rocket which put 12 men on the moon and Skylab into orbit hasn't been built in 44 years. Contrary to popular belief the plans for these beast DO still exist, but they are in obsolete computer formats and of limited use.
You see, the Apollo program was so rushed that a lot of the little 'tweaks' that were found necessary to keep the rocket from failing. This was not fully appreciated until the '80s when NASA and USAF engineers noted that there were holes drilled and pieces added to some of the F-1s in museums...holes and fiddly bits that weren't on the plans. The engines were exploding during tests and the production crew did some trial and error modifications until the "splodies" stopped. Additional tweaks were added at the plant to facilitate production, so the F-1 plans are actually plans for an inefficient kerosene/LOX bomb.

Well, engineers in Huntsville have taken apart and are restoring some of these engines, which were discovered to be in remarkably good shape. This time making a note of Every.Single.Part. And. Hole. The plan is to do a computer model of the engine that is accurate, but they need to ensure that they are building it from a working engine...so.....

That's just a test of the engines gas generator from last year...
This project is the brainchild of Marshall Spaceflight center engineers who felt that they ought to DO something with the dozen or so F-1s lying around the research center. They've been calling in other rocketry companies to observe and consult. In addition they've been bringing in the few surviving Apollo engineers to work on this interesting side project...which has resulted in a tentative design and proposal for the F-1B

This is not as silly as it sounds. One of the things about the F-1 that was discovered back in the 60's was that, due to its very conservative design it was actually pretty re-useable and it was felt it could be made completely so with a few tweaks. F-1s were considered for several early space shuttle designs propelling reusable flyback boosters.

The mighty F-1 may yet again spew pillars of fire for the chariots of explorers.

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Of course letting Aerojet to develop AJ-500 would be much too efficient and market oriented, and do nothing to make something to do for the Marshall Center in service of the government unnecessary launcher, which only exists because it's mandated by U.S. Senate.

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Keeping ones design staff occupied with actually designing and reverse engineering things is pretty important. Refurbishing engines that were laying about and tweaking them seems to be a decent idea....especially since they are bringing in private contractors to observe and learn. The rocketdyne poatents have probably expired by now so this could serve to provide the industry with a "public domain" heavy lift engine. I'm not convinced such a big rocket is needed, but some people like Zubrin are convinced it is a necessity for a manned Mars program. I'd rather not have them re-invent the wheel.

I'm all for keeping engineers current, especially since people at Marshall haven't done anything flying in decades -- enough for a generational turnover to wipe any expertise. Even Mike Griffin admitted that Ares I was basically a rocket with training wheels for them before designing Ares V (now SLS). The problem, however, is how all they build in the end is useless. If we just fire all of them and keep a skeletal staff just to steward the irreplaceable infrastructure such as test stands, the loss of expertise and capability is going to be minimal, as far as America is concerned. But the people bumped off government payroll might just find a productive employment however. Even being a WalMart greeter is more productive than designing SLS (in this case its boosters).

I relish in the thought that Marshall could kick ATK in the gonads if they ever make this F-1B work, but if it were possible to end the whole boondoggle, I would.